ARKit 如何给SCNNode贴Gif图片

最近在研究如何在SCNNode上加载Gif图片，总结出两种解决方案。
首先介绍下SCNMaterial，它是SCNNode的材质属性，可以通过它给Node添加各种皮肤材质，根据官方文档，SCNMaterial的contents可以用UIColor、UIImage、CALayer、NSURL等等，真是无敌了，虽然UIView没有提及，但是我自己试验之后也是可以的，不过加载Gif会堵塞UI线程。

Specifies the receiver's contents. This can be a color (NSColor, UIColor, CGColorRef), 
an image (NSImage, UIImage, CGImageRef), a layer (CALayer), a path (NSString or NSURL), 
a SpriteKit scene (SKScene), a texture (SKTexture, id or GLKTextureInfo), 
or a floating value between 0 and 1 (NSNumber) for metalness and roughness properties.

png

一 通过将Gif图片转成MP4文件

需要先将Gif图片转成MP4文件，存在缓存中，通过AVPlayer即可加载，转mp4还是有些耗时，建议后台进行预处理。

//此处贴出关键代码
let fileData:NSData = model.getFileData()
let tempUrl = URL(fileURLWithPath:NSTemporaryDirectory()).appendingPathComponent("temp.mp4")
GIF2MP4(data: fileData as Data)?.convertAndExport(to: tempUrl, completion: {
    let playerItem = AVPlayerItem.init(url: tempUrl)
    let player = AVPlayer.init(playerItem: playerItem)
    player.play()
              
    material.diffuse.contents = player
    })
}

func convertAndExport(to url :URL , completion: @escaping () -> Void ) {
        outputURL = url
        prepare()
        
        var index = 0
        var delay = 0.0 - gif.frameDurations[0]
        let queue = DispatchQueue(label: "mediaInputQueue")
        videoWriterInput.requestMediaDataWhenReady(on: queue) {
            var isFinished = true
            
            while index < self.gif.frames.count {
                if self.videoWriterInput.isReadyForMoreMediaData == false {
                    isFinished = false
                    break
                }
                
                if let cgImage = self.gif.getFrame(at: index) {
                    let frameDuration = self.gif.frameDurations[index]
                    delay += Double(frameDuration)
                    let presentationTime = CMTime(seconds: delay, preferredTimescale: 600)
                    let result = self.addImage(image: UIImage(cgImage: cgImage), withPresentationTime: presentationTime)
                    if result == false {
                        fatalError("addImage() failed")
                    } else {
                        index += 1
                    }
                }
            }
            
            if isFinished {
                self.videoWriterInput.markAsFinished()
                self.videoWriter.finishWriting() {
                    DispatchQueue.main.async {
                        completion()
                    }
                }
            } else {
                // Fall through. The closure will be called again when the writer is ready.
            }
        }
    }

---

二 通过关键帧动画来实现

//获取Gif图片数据
let fileData = model.getFileData()
let animation : CAKeyframeAnimation = createGIFAnimationYY(data: fileData)

//通过CALayer给material赋值                
let layer = CALayer()
layer.bounds = CGRect(x: 0, y: 0, width: imageW, height: imageH)
layer.add(animation, forKey: "contents")

//直接将CALayer赋值给material，Gif只会显示右下角1/4                
let tempView = UIView.init(frame: CGRect(x: 0, y: 0, width: imageW, height: imageH))
tempView.layer.bounds = CGRect(x: -imageW/2, y: -imageH/2, width: imageW, height: imageH)
tempView.layer.addSublayer(layer)
material.diffuse.contents = tempView.layer

转成关键帧动画，由于有些Gif很大，帧数很多，此处我做了一些内存优化，极端情况内存占用优化至之前的1/10，这种方法相比于上一种加载速度会更快一点，但内存占用稍大。

func createGIFAnimationYY(data:NSData) -> CAKeyframeAnimation {
    
    let image = YYImage.init(data: data as Data)
    let bytes = Int.init(bitPattern: (image?.animatedImageBytesPerFrame())!)
    let nFrame = Int.init(bitPattern: (image?.animatedImageFrameCount())!)
    let bufferSize = Float(bytes*nFrame)
    let total = getDeviceMemoryTotal();
    let free = getDeviceFreeMemory();
    print("start: bufferSize:",bufferSize," totalMem: ",total," free: ",free)
    var maxSize = min(total*0.2, free!*0.6)
    maxSize = max(maxSize, Float(BUFFER_SIZE))
    if maxSize > bufferSize {
        maxSize = bufferSize
    }
    var maxBufferCount = Int(maxSize / Float(bytes))
    if maxBufferCount < 1 {
        maxBufferCount = 1
    } else if maxBufferCount > 256 {
        maxBufferCount = 256
    }
    //实际帧数跟优化帧数比值
    let ratio = Float(nFrame)/Float(maxBufferCount)
    
    // Total loop time
    var time : Float = 0
    
    // Arrays
    var framesArray = [AnyObject]()
    var tempTimesArray = [NSNumber]()
    
    for i in 0..

效果图

demo.gif

原文链接：https://www.jianshu.com/p/f5d13540c08d